Water glass is a soluble alkali metal silicate material, which is composed of alkali metal oxides and silicon dioxide, also known as sodium silicate. Water glass can be divided into sodium water glass and potassium water glass according to the types of alkali metals, and their molecular formulas are Na2O.nSiO2 and K2O.nSiOz respectively. The coefficient n in the formula is called the modulus of water glass, which is the molecular ratio (or molar ratio) of silicon oxide and alkali metal oxide in water glass. The modulus of water glass is an important parameter of water glass, which is generally between 1.5-3.5. The larger the modulus of water glass, the more difficult it is for solid water glass to dissolve in water. When n is 1, it can be dissolved in warm water; when n increases, it needs hot water; when n is greater than 3, it needs more than 4 atmospheres of steam to dissolve. The larger the modulus of water glass, the more silica content, the higher the viscosity of water glass, the easier it is to decompose and harden, and the higher the adhesion.
There are two methods to produce sodium silicate: dry method and wet method. The dry method takes quartzite and soda ash as raw materials, grinds and mixes them evenly, then melts them in a furnace at 1300- 1400℃, and reacts according to the following formula to generate solid water glass, which is dissolved in water to prepare liquid water glass.
In wet production, quartz powder and caustic soda are used as raw materials and autoclaved in a high-pressure steamer with 2-3 atmospheres to directly generate liquid sodium silicate.